content: /*
   * Copyright 2016 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package hu.akarnokd.agera;
  
  import android.support.annotation.NonNull;
  
  import com.google.android.agera.Updatable;
  import com.google.android.agera.UpdateDispatcher;
  
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.concurrent.atomic.AtomicLong;
  
  /**
   * Replays all update() signals to Updatables that have been received
   * by the ReplayingDispatcher.
   */
  public final class ReplayingDispatcher extends AgeraTracking<ReplayingUpdatable> implements UpdateDispatcher {
  
      final AtomicLong count = new AtomicLong();
  
      @NonNull
      @Override
      protected ReplayingUpdatable createWrapper(@NonNull Updatable updatable) {
          return new ReplayingUpdatable(updatable, this);
      }
  
      @Override
      protected void onAdd(@NonNull Updatable updatable, @NonNull ReplayingUpdatable wrapper) {
          wrapper.drain();
      }
  
      @Override
      protected void onRemove(@NonNull Updatable updatable, @NonNull ReplayingUpdatable wrapper) {
          wrapper.cancelled = true;
      }
  
      @Override
      public void update() {
          count.getAndIncrement();
          for (ReplayingUpdatable bu : map.values()) {
              bu.drain();
          }
      }
  }
  
  final class ReplayingUpdatable
  extends AtomicInteger {
      final Updatable actual;
  
      final ReplayingDispatcher parent;
  
      volatile boolean cancelled;
  
      long index;
  
  
      ReplayingUpdatable(Updatable actual, ReplayingDispatcher parent) {
          this.actual = actual;
          this.parent = parent;
      }
  
      void drain() {
          if (getAndIncrement() != 0) {
              return;
          }
  
          int missed = 1;
  
          for (;;) {
  
              long i = index;
              long r = parent.count.get();
  
              while (i != r) {
                  if (cancelled) {
                      break;
                  }
                  actual.update();
                  i++;
              }
  
              if (cancelled) {
                  break;
              }
  
              index = i;
  
              missed = addAndGet(-missed);
              if (missed == 0) {
                  break;
              }
          }
      }
  
  }
  
  